Python String Formatting: % Operator and format() Method

Python String Formatting

Python provides two main syntaxes for formatting output: the C‑style % operator (called Formatting Expression) and the format() method (String Formatting Method Calls). Both allow insertion of values into strings with various specifiers.

1. Integer Output

The % operator supports several integer specifiers:

Specifier

Description

Note

%o

Octal

oct

%d

Decimal

dec

%x

Hexadecimal

hex

print('%o' % 20)   # octal
print('%d' % 20)   # decimal
print('%x' % 24)   # hexadecimal

2. Float Output

Common float specifiers include:

Specifier

Description

%f

Fixed‑point with six decimal places

%e

Scientific notation with six decimal places

%g

Uses fixed‑point or scientific notation to keep six significant digits

print('%f' % 1.11)          # 1.110000
print('%.1f' % 1.11)        # 1.1
print('%e' % 1.11)          # 1.110000e+00
print('%.3e' % 1.11)        # 1.110e+00
print('%g' % 1111.1111)    # 1111.11
print('%.7g' % 1111.1111)   # 1111.111
print('%.2g' % 1111.1111)   # 1.1e+03

3. String Output

String specifiers allow alignment and truncation:

Specifier

Description

%s

String

%10s

Right‑aligned in a field of width 10

%-10s

Left‑aligned in a field of width 10

%.2s

Truncate to 2 characters

%10.2s

Width 10, truncate to 2 characters

print('%s' % 'hello world')          # hello world
print('%20s' % 'hello world')        #          hello world
print('%-20s' % 'hello world')       # hello world          
print('%.2s' % 'hello world')        # he
print('%10.2s' % 'hello world')      #         he

4. format() Method

The format() method uses curly braces as placeholders and offers greater flexibility.

Basic Usage

print('{} {}'.format('hello', 'world'))                     # hello world
print('{0} {1}'.format('hello', 'world'))                     # hello world
print('{0} {1} {0}'.format('hello', 'world'))                 # hello world hello
print('{1} {1} {0}'.format('hello', 'world'))                 # world world hello

Advanced Usage

Alignment specifiers:

print('{:<10s} and {:>10s}'.format('hello', 'world'))   # hello      and      world
print('{:^10s} and {:^10s}'.format('hello', 'world'))      #   hello   and   world

Precision and width:

print('{:.2f}'.format(1.123))               # 1.12
print('{:>10.2f}'.format(1.123))            #       1.12

5. Miscellaneous

Automatic Newline

for i in range(0,3):
    print(i)
# Output:
0
1
2

No Newline

for i in range(0,3):
    print(i, end='')
# Output:
012

6. Advantages of format() over %

No need to consider data types.

Single argument can be reused multiple times; order can be changed.

Highly flexible padding and alignment options.

Officially recommended; the % style is deprecated in newer Python versions.

7. Light‑hearted Closing

A short eye‑exercise reminder and a note about the FunTester public account.